High contents of chromium, molybdenum and/or tungsten provide a high tempering resistance to high speed steels which is the fundamental factor for the good properties of these steels when used for cutting tools. The said elements, and particularly molybdenum and tungsten, also contribute to provide a high hardness and good wear resistance to the steel by combining with carbon in the steel to form M.sub.6 C-carbides. Modern high speed steels also contain high contents of vanadium which on one hand exist dissolved in the matrix and on the other hand form MC-carbides which are harder than the M.sub.6 C-carbides and therefore have been considered to be desirable with reference to the demand on good wear resistance. In conventional steel production these MC-carbides tend to be comparatively large because of the slow cooling in ingot moulds, These large MC-carbides have a strong detrimental effect upon the grindability of the steel.
In powder metallurgical production of high speed steels, quickly solidified metal powder is subjected to compaction at a high pressure and high temperature to full density. The carbides in the metal powder are originally very small and uniformly distributed in the steel matrix owing to the quick cooling in the powder production. However, because of the high temperature during consolidation, the carbides grow. If this growth exceeds a certain size, the properties of the steel are impaired, in the first place its grindability, so that 3 microns has been considered to be the maximal size of these carbides which can be tolerated. In order to achieve this goal, heating during the consolidation of the powder steel has been performed at a temperature not exceeding approximately 1150.degree. C. in view of the fact that higher temperatures being about a considerably faster carbide growth. This, however, reduces productivity.
Similar problems also arise in the powder metallurgical production of vanadium-containing cold work steels of the type which contain relatively high proportions of chromium and carbon, Besides M.sub.7 C.sub.3 -carbides, these steels (because of the vanadium content) usually will also contain MC-carbides.